In the broiler industry for raising poultry, precisely chickens, and especially broilers, improvements and developments have been made essentially in the breeding technique for phyletic lines of broilers and in the rearing technique for increasing the growth rate of broilers. Above all, much emphasis is put on the growth rate and the feed conversion rate in the method of rearing broilers, and high-calorie feed and pellet-like feed have become used for rearing broilers. Use of such feed has made it possible to increase the growth rate and the feeding efficiency, but on the other hand, has brought about some problems. Specifically, too much increase in the growth rate of broilers during the rearing period could not be followed by sufficient body metabolic functions such as the cardiac function, etc., and the imbalance therebetween has increased the death rate, thereby lowering the raising rate and the productivity to cause great economic damage to the broiler industry.
One essential cause of death of broilers from the imbalance between the growth rate and the development of cardiac functions is ascites. Broilers having been fed with high-calorie feed could grow rapidly, but it is known that, in those, the incidence of ascites is high. In addition, depending on the raising condition, many broilers often have ascites in winter or at highlands, or in raising with high stocking density of chicks.
To lower the incidence of ascites in broilers, a raising method may be taken for well controlling the growth rate to thereby make the development of the cardiac function and the growth rate balanced, which, however, is not favorable from the economic viewpoint.
Some techniques of using coenzyme Q have been developed for the means of preventing broiler ascites while keeping a high growth rate of broilers in some degree, two of which mentioned below are known.
I. Quinones containing coenzyme Q are administered to broilers to prevent them from having ascites, thereby increasing the raising rate (Japanese Patent Application Laid-Open (JP-A) Hei-6-287136).
II. Feed containing coenzymes Q.sub.9 and Q.sub.10 is used to prevent ascites and sudden death syndrome (JP-A Hei-7-123928)
They say that, in the proposed techniques, coenzymes Q.sub.9 and Q.sub.10 are effective for preventing ascites, but no sufficient discussions have been made for further increasing the growth rate of broilers according to those techniques.
In other words, no attempt has heretofore been made at using coenzyme Q for preventing ascites of broilers while keeping a suitable raising rate so as to improve the growth rate, for example, by fully analyzing the growing process of broilers to thereby design a suitable feed composition and a suitable feeding method that indicate the combination of feed and coenzyme Q to be fed to broilers with respect to the degree of metabolizable energy to be derived from the feed and to the stage at which the coenzyme Q-containing feed shall be applied to broilers during the rearing period.
The present invention has been made from the viewpoint noted above, and its object is to provide a feed composition for broilers with which broilers being fed can be fully prevented from having ascites and can grow rapidly, and which therefore makes it possible to increase the growth rate of broilers and to shorten the growing period thereof, and also to provide a feeding method for broilers where is used the composition to attain high productivity.
The term "raising rate" as referred to herein indicates the ratio of the number of the living broilers counted at the end of the rearing period to the number of all broilers in the initial stage (=number of all broilers in the initial stage-number of broilers died during the rearing period).